The Celestron 2a? to 1.25a? Adapter with Twist-Lock was designed for visual observers who use both 2a? and 1.25a? eyepieces regularly and need a quick adapter to use with the 2a? barrel.A The twist-lock eyepiece holder secures eyepieces while keeping them centered in the adapter, providing best opto-mechanical alignment between the telescope and eyepiece. Unlike traditional thumb screws, the twist-lock cannot scratch or engrave the barrel of your eyepieces. The adapter has an integrated 1.25a? barrel stop that prevents 1.25a? accessories with long barrelsA from damaging the mirror.A All the adaptera?s mechanical parts are made of machined black anodized aluminum, except the twist-lock rings, which are orange anodized for visibility. Save Time and Money when using Eyepiece Filters If you want to look at an object under different eyepiece magnification but keep the same eyepiece filter, thread your 2a? eyepiece filters to the barrel of the adapter. Since this adapter accepts 2a? filters, you can also save money by buying fewer 1.25a? eyepiece filters.